Line cutting devices

ABSTRACT

A cutting device adapted to cut flexible line such as cable or wireline in a well includes an elongated tubular body having an axial channel arranged to receive the cable to be cut, a fixed blade member and a rotatable blade member each having a cutting edge located on respective opposite sides of the channel, and an actuating member movable in the body and engageable with the rotatable blade member to cause rotation thereof in response to the application of longitudinal force, said blade members each having arcuate cutting edges initially surrounding half-sections of the cable. Movement of said actuating member and said rotatable blade member causes a locking wedge to grip the cable above the cut so that the device can be removed from the well with the cable.

United States atent Ribeyre et al.

[ 1 Dec. 16, 1975 LINE CUTTING DEVICES [75] Inventors: Jean-Paul Ribeyre; Claude Marty,

both of Cesson, France [73] Assignee: Schlumherger Technology Corporation, New York, NY.

[22] Filed: Sept. 19, 1974 [21] Appl. No.: 507,183

[52] US. Cl l66/54.6; 114/221 A [51] Int. Cl. E21B 29/00 [58] Field of Search 166/545, 54.6, 55.1; 43/172; 102/212; 114/221 A, 221 R [56] References Cited UNITED STATES PATENTS 692,816 2/1902 Bell 166/546 969,571 9/1910 Spang 1 166/546 1,018,274 2/1912 Sheehan et al. l66/54.6

1,596,608 8/1926 Gallman et al. t 166/546 1,610,699 12/1926 Montgomery 166/546 2,185,303 l/1940 Kinley 166/546 2,495,953 l/l950 Austin 166/546 2,794,619 6/1957 Lawrence et al. 166/546 Primary Examiner-David H. Brown Attorney, Agent, or Firm-David L. Moseley; Stewart F. Moore; William R. Sherman [5 7 ABSTRACT A cutting device adapted to cut flexible line such as cable or wireline in a well includes an elongated tubular body having an axial channel arranged to receive the cable to be cut, a fixed blade member and a rotatable blade member each having a cutting edge located on respective opposite sides of the channel, and an actuating member movable in the body and engageable with the rotatable blade member to cause rotation thereof in response to the application of longitudinal force, said blade members each having arcuate cutting edges initially surrounding half-sections of the cable. Movement of said actuating member and said rotatable blade member causes a locking wedge to grip the cable above the cut so that the device can be removed from the well with the cable.

13 Claims, 7 Drawing Figures US. Patent Dec. 16, 1975 Sheet1of3 3,926,252

42 FIG. 7A

U.S. Patent Dec. 16, 1975 Sheet 3 of 3 3,926,252

FIG. 5 l

zliH

LINE CUTTING DEVICES This invention relates to line cutting devices, and is particularly concerned with cutting devices adapted to cut a flexible wire or cable upon which a well tool is suspended in a borehole.

Many well operations involve the use of a flexible line or cable to position instrumentalities in the well bore. For example, most exploration and production logging services are carried out with one or more sensing devices that are run into the well on an armored electric cable to enable surface readout of data. Other well service operations such as temperature and pressure surveys, and the emplacement and removal of various production controls and gas lift valves, are carried out through use of a solid steel measuring line commonly called a wireline or slick-line. As those familiar with this art will readily appreciate, such instrumentalities and tools on occassion may become stuck or lodged under circumstances that require a fishing operation to be employed to remove them from the well.

To this end, many well logging and wireline service tools are provided with a fishing neck over which a specially adapted fishing tool can be lowered, the fishing tool being adapted to grip the fishing neck firmly to facilitate withdrawal of the tool without substantial damage thereto. However, in some circumstances, it is desirable that the cable or line be cut from the tool and removed from the borehole, before the fishing tool is used. In this case, it is essential that the cable or line be cut as close to the fishing neck as possible, in order that the remaining piece attached to the tool shall not interfere with the engagement of the fishing neck by the fishing tool.

To perform the cutting operation, a cutting device is slidably fitted to the cable at the top of the borehole, and allowed to slide down the cable under the influence of gravity until it reaches the well tool. One known type of such a cable cutting device, described in US. Pat. No. 3,073,388, comprises a body slidably inserted over the cable and a pivotally mounted blade member which cooperates with a cutting edge of the body disposed on the other side of the cable, to cut the cable on top of the well tool. The blade member is actuated by an explosive charge fired by a timing mechanism. After the cable is severed, the blade member clamps the cable against a wall of the body. A second known type of cutting device comprises a pair of slidable blade members, which are initially disposed on opposite sides of the cable and whose cutting edges come together in the middle portion of the cable to cut the cable. The blade members are forced toward each other by a longitudinally movable sleeve driven downwardly by the impact force of ajar member when the cutting device is on top of the well tool.

Both of these known types of cable cutting devices suffer from the disadvantage that a considerable proportion of the energy imparted to the movable blade member is dissipated in crushing the cable by the rectilinear cutting edges prior to completing the cut. Additionally, in the former type, there may be a vertical gap between the two cutting edges due to the pivotal mounting of the movable blade member, while in the latter type, the cutting edges have to be well sharpened and without any lateral gap between them for performing correctly their cutting action.

It is therefore a primary object of the present invention to provide a cable cutting device suitable for cutting the cable of a well tool, at a location close to the tool, in a more efficient manner than is achieved by the aforementioned known types of cable cutting devices.

It is a further object of the present invention to provide a cable cutting device having blade members which can perform a greater number of cuts than can be achieved with the known types of cable cutting device.

It is sometimes necessary to perform the cutting operation in a borehole having a gas-liquid interface therein above the level at which the cut is required. When the cutting device slides down the cable, it is abruptly decelerated on striking this interface. In the known types of cutting tool, this abrupt deceleration can result in operation of the cutting device, thereby producing the cut in the wrong place in the cable.

It is yet another object of the present invention to provide a cable cutting device capable of being used in boreholes which have a gas-liquid interface therein without premature operation of the device as it passes through the interface.

Another object of the invention in one of its more specific forms is to provide a cable cutting device which automatically locks itself after cutting to the portion of the cable cut from the well tool, to facilitate withdrawal of the cutting tool from the borehole by this portion of the cable.

These and other objects are attained in accordance with the present invention through the provision of a cutting device including an elongated body having a longitudinally extending channel therein for slidably receiving the cable or line to be cut. A first blade member fixed in the lower end of the body has a first surface defining a first cutting edge, and a second blade member which is movable within the body has a second surface slidably mounted on said first surface and defining a second cutting edge movable along a path intersecting the channel. An actuating member responsive to a longitudinally applied force is movable into engagement with the second blade member to produce the sliding movement thereof. The blade members are arranged such that the path of the second blade member defined by the first surface is substantially perpendicular to the longitudinal axis of the channel and the cutting edges have respective recessed middle portions disposed on opposite sides of the channel for enclosing the channel prior to a cutting operation. During the cutting operation the cable is caught by both cutting edges in all directions around its periphery and no en ergy is dissipated in crushing the cable.

Locking means responsive to the movement of the actuating member locks the device on the severed cable thereby enabling the cutting device to be retrieved by the cable from the well. Such locking means may comprise a wedgeshaped locking member slidable against upwardly and inwardly inclined surface of the actuating member which forces the locking member into clamping engagement with the cable or line in the channel during downward movement of the actuating member. In a preferred embodiment, the locking member extends downwardly into engagement with the second blade member for maintaining the second blade member on the opposite side of the channel prior to the cutting operation, and is driven relatively upwardly by rotation of the second blade member to assist in clamping the line as mentioned above.

The locking member may be secured to the actuating member by a shear pin. In liquid filled wells a heavy inertial mass is secured to the operating member for shearing the pin upon deceleration of the body when the cutting device contacts the well tool. According to another important feature of the invention, for use in wells having a gas-liquid interface, the heavy inertial mass is dropped along the cable independently and above the body to strike an upwardly extending portion of the actuating member thereby shearing the pin to perform the cutting and clamping operation.

The present invention has otherfeatures, objects and advantages which will become more clearly apparent in connection with the following detailed description of various embodiments thereof, taken in conjunction with the accompanying drawings, in which:

FIGS. 1A and 1B show in axial cross-section one embodiment of a cutting device in accordance with the present invention, with the various components of the device in the positions they occupy prior to a cutting operation;

FIG. 2 is an exploded perspective view of the blade members of the present invention;

FIG. 3 is a cross-section taken on line 33 of FIG. 1B;

FIG. 4 is a perspective view of another part of the cutting device of FIG. 1;

FIG. 5 shows the operative position of various parts of the cutting device after it has performed a cutting operation; and

FIG. 6 is a cross-sectional view of another embodiment of a cutting device in accordance with the present invention, also with the components of the device in the positions they occupy prior to a cutting operation.

Referring initially to FIGS. 1A and 1B, a line cutting device constructed in accordance with the principals of the present invention is indicated generally at 10, and is adapted for use in cutting a flexible line 12 such as a stranded cable having a diameter up to one quarter of an inch. The line 12 suspends a well tool (not shown) in a borehole under circumstances where the tool has become stuck and it is desirable to cut the line loose. The cutting device is designed to make the cut at a point close to the well tool, as will hereinafter become apparent, in. order to facilitate retrieval of the well tool by means of conventional fishing techniques and is particularly suitable for use in boreholes containing a gas-liquid interface above the level at which it is desired to cut the cable 12.

The cutting device 10 comprises an elongated, substantially cylindrical, hollow body 14, having an axial channel 16 extending longitudinally therethrough. The body 14 comprises upper and lower portions 18 and 20 which are threaded together at 22. The body portions 18, 20 have slots 24, 26 therein, with each slot extending longitudinally for the whole length of the respective portion and radially from the channel 16 to the outside. The slots 24, 26 are angularly aligned with each other to enable the body to be fitted onto the line 12.

The interior of the lower body portion 20 contains two blade members 28, 30 adjacent the lower end 32 thereof. The blade member 28 has a flat base 34, which is supported by a radially inwardly projecting shoulder 36 provided in the body portion 20. The external surface 38 of the blade member 28 is generally cylindrical, as best seen in FIG. 2, and fits coaxially inside the body portion 20. A slot 40 extends radially into the blade member 28 throughout the length thereof and is radially aligned with the slot 26. The inner region 42 of the slot 40 is aligned with, and therefore forms a continuation of, the channel 16. The blade member 28 has a concave part-cylindrical upper surface 44, the axis of which extends perpendicularly through the axis of the channel 16. The portion of the surface 44 which intersects the region 42 of the slot 40 is thus substantially perpendicular to the axis of the channel 16, and defines a substantially semi-circular cutting edge 46. Two pins 43 and 45 are fitted in spaced apart vertical holes passing through the blade member 28 and have upper end portions projecting above the surface 44.

The blade member 30 is substantially semi-circular in cross-section, and has a substantially flat upper surface 49 with an upwardly directed concave portion 51 and a convex part cylindrical lower surface 50. The surface 50 is complementary to and supported on the surface 44, so that the blade member 30 is rotatable with respect to the blade member 28 about the common axis of the surfaces 44, 50. A slot 52 extends radially into the blade member 30, this slot being angularly displaced by l80 with respect to the slot 40. In the position of the blade member 30 illustrated in FIG. 1B, the upper surface 49 of the blade member 30 is inclined to a plane perpendicular to the axis of the body portion 20, so that one end 53 of the surface 49 stands above the blade member 28, and the radially inner region 54 of the slot 52 is aligned with the radially inner region 42 of the slot 40. The region 54 of the slot 52 thus also forms a continuation of the channel 16 and the portion of the surface 50 which intersects the region 54 is also substantially perpendicular to the axis of the channel 16 and defines another substantially semi-circular cutting edge 56. The cutting edge 56 co-operates with the cutting edge 46 to enclose completely a transverse cross-section of the line 12 as will hereinafter be described. Downwardly facing flat shoulders 58 to either side of the blade member 30 engage the pins 43 and 45 of the blade member 28 in the position illustrated in FIG. 1B and prevent the blade member 30 from rotating any further in the counter clockwise direction.

The interior of the body 14 receives an axially movable cylindrical sleeve 60, of an impact-withstanding material, which is coaxial therewith and which is held longitudinally spaced above the blade members 28, 30 as will hereinafter be explained. The sleeve 60 comprises upper and lower sleeve portions 61, 62 which are threaded together at 63. The sleeve portions 61, 62 have respective slots 69 and 64 formed therein, with each slot extending longitudinally throughout the length thereof and radially from the interior to the exterior of the sleeve portion. The slot 64 is aligned with the slot 24 in the body portion 18, while the slot 69 is angularly displaced by 90 with respect to the slots 24 and 64. The sleeve portion 62 also has transversegrooves 65 and 65' extending on each side of slot 64 as shown in FIG. 3, with each groove being open at its upper end but closed at its lower end by a shoulder 67.

The internal surface 66 of the sleeve portion 62 opposite the radial slot 64 is flat and inclines in the upward direction towards the axis of the sleeve portion. The surface 66 bears upon a correspondingly inclined rear surface 68 of a wedge-shaped member 70. The member 70 extends substantially parallel to the axis of the sleeve portion 62 on one side of the channel 16, and projects downwardly from the sleeve portion 62 into contact with the concave portion 51 of the upper surface 49 of the blade member 30. The wedge member 70 is movable with respect to the sleeve portion 62, but is held in the position illustrated in FIG. 1B by means of a shear pin 73 which extends through apertures in the cylinder portion 62. The wedge 70 and the shear pin 73 therefore serve to hold the sleeve 60 above the blade members 28, 30, and the wedge 70 additionally function to hold the blade member 30 in the position shown in FIG. 1B.

An elongated key 74 shown in detail in FIG. 4 is mounted in the slots 64 and 65 in the sleeve portion 62. The key 74 comprises a main portion 75 dimensioned to fit in the grooves 65 and a downwardly projecting offset portion 76 of smaller thickness dimensioned to fit into the slot 26 of the lower body portion 20 as well as in slot 40 of the blade member 28. As illustrated in FIG. 1B, the main portion 75 of the key 74 is maintained in grooves 65 of the sleeve portion 62 between the shoulders 67 and the lower end face of the sleeve portion 61, whereas the projection of the portion 76 into the slots 26 and 40 of the lower body portion 20 and of the blade member 28 respectively, prevents the lower body portion 20 and the fixed blade member 28 from rotating relative to the actuating sleeve 60.

As shown in FIG. 1A, the upper end of the sleeve portion 61 extends above the top surface of the body 14 and has an outward directed flange 78 of greater diameter than the bore of the body. A screw 80 having threaded ends 81 is located in an offset transverse hole in the flange 78 and is perpendicular to, and radially spaced from the axis of the sleeve portion 61. The screw 80 can of course by removed to enable fitting the member 60 onto the line 12, and when in place as shown maintains the line within the channel 16.

The cutting device as thus far described is operated by the impact of a hammer or go-devil of simple form, and for the sake of completeness this part is 'shown at 82 in FIG. 1A. The go-devil 82 comprises a relatively heavy tubular body 84 having an axial channel 85 therethrough, the body 84 being provided with threaded caps 86 and 87 screwed into each end. The caps 86 and 87 each have radially directed slots 88 and 89 therein that open the bores 90 and 91 to the outside, and the body 84 also has a radially directed longitudinal slot extending from the channel 85 to the outside. Thus it will be apparent that caps 88 and 89 can be screwed loosely onto the body 84 with the slots 88, 89 aligned with the body slot to enable the go-devil to be positioned on the line 12, whereupon the caps are tightened down to misalign the slots and thus cause the body 84 to be retained on the line.

It will be appreciated that the end of the cable 12 at the top of the borehole is normally wound around and secured to the drum of a winch, and so is not freely accessible. In operation, therefore, the cable cutting device 10 is assembled around the cable 12 at the top of the borehole in the following manner. The blade member 30 and the key 76 are removed, and the cable 12 is passed into the slots 26, 40 in the body portion and blade member 28 respectively. Then the slot 52 in the blade member 30 is offered up to the cable 12 to permit the blade member 30 to be mounted on the blade member 28 in the position shown in FIG. 1B. The lower sleeve portion 62, including the wedge 70 which is held in position by the shear pin 73 is then fitted onto the cable 12 above the body portion 20 by way of the slot 64 and correctly aligned with respect to the blade members 28, 30. The key 74 then is inserted into the grooves 65 and the downwardly projection portion 76 is inserted in slots 26 and 40 of the lower body portion 20 and blade member 28 respectively. Next the upper body portion 18 is fitted to the cable 12 above the sleeve portion 62 utilizing the slot 24, and the threads 22 are screwed together. The upper sleeve portion 61 with the screw 80 removed is then fitted to the cable 12 above the body portion 18 by way of the slot 69 and the threads 63 of the sleeve portions 61, 62 are screwed together to complete the sleeve 60. Finally, the screw 80 is threaded in the flange 78. At this point the cable 12 extends longitudinally through the body 14 within the channel 16, and passes between the blade members 28, 30, and between the wedge and the key 74 inside the sleeve 60. The relative angular dispositions of the slots 24, 26, 40, 52, 64 and 69 ensure that the cable 12 is retained in the channel 16.

When the assembly of the cutting device 10 is complete, it is allowed to slide down the cable 12 into the well under the influence of gravity. It will be recalled that the cutting device 10 is intended for use in a borehole having a gas-liquid interface, which produces a substantial deceleration of the cutting device as the device passes therethrough. However, the weight of the components of the cutting device 10, particularly of the sleeve 60, is arranged to be sufficiently small that the shear pin 73 is not sheared by this deceleration. The cutting device 10 continues its descent of the cable 12 until it reaches the stuck tool, where it experiences another deceleration. Again, the weight of the components is such that the shear pin 73 is not sheared, so that the cutting device 10 comes to rest on the top of the tool with its components disposed as shown in FIGS. 1A and 1B.

The go-devil 82 is then assembled around the line 12 at the top of the borehole in a manner analogous to the assembly of the cutting tool 10, and allowed to slide down the cable into the well. When the go-devil 82 reaches the cutting tool 10, it strikes the upper surface of the sleeve 60. Since the go-devil is relatively heavy, typically about 12 kilograms, it applies a substantial longitudinal impact force to the sleeve 60 which is sufficient to shear the shear pin 73. The sleeve 60 therefore moves downwardly with respect to the body 14, and strikes the upstanding end 53 of the upper surface 49 of the blade member 30. The impact of the sleeve 60 on the blade member 30, and the continued downward movement of the sleeve, produce clockwise rotation of the blade member 30 with respect to the blade member 28. The blade member 30 thus rotates to the position illustrated in FIG. 4, during which its cutting edge 56 passing through the channel 16 substantially perpendicularly to the axis thereof and co-operates with the cutting edge 46 of the blade member 28 to cut the cable 12 substantially perpendicularly to its axis. Throughout the cutting action the cable is maintained laterally in a horizontal direction perpendicular to the movement of the blade member 30 by the semi-circular-shaped cutting edges 46 and 56. Since the blade members 28, 30 are close to the bottom of the body 14, only a short length of cable, typically less than two inches, is left attached to the well tool.

During the downward movement of the sleeve 60,- the internal inclined surface 66 thereof cooperates with the inclined surface 68 of the wedge 70 to move the wedge to the right as viewed in FIG. 4 and towards the key portion 74. Moreover, as the blade member 30 performs its rotational movement, the concave portion 51 of its upper surface 49 pushes the lower end of the wedge 70 upwardly, thereby producing further rightward movement of the wedge 70 and firmly clamping the severed upper part of the line 12 between the wedge and the key 74. The severed cable is then removed from the well by means of the aforementioned winch, and brings the cutting device 10 out with it to enable a conventional fishing operation to be performed to recover the stuck tool. Upward force on the line 12 will cause the wedge 70 to grasp the line ever more tightly.

By virtue of the use of the relatively movable blade members 28, whose respective arcuate cutting edges 46 and 56 surround the cable in a plane substantially perpendicular to the axis of the cable 12, a clean and efficient cut is made through the cable 12. A given pair of the blade members 28, 30 can therefore be used for many cuts, before sharpening or replacement is required.

A modified form of cutting device is shown in FIG. 6 and indicated generally at 100. Inasmuch as the device 100 has many components in common with the cutting device 10 already described, these common components are given the same reference numerals as were used in connection with FIGS. 1 to 5, and only the points of difference will be described. Thus the cutting device 100 of FIG. 5 is intended for one-step operation in boreholes having no gas-liquid interface, and to this end the go-devil 82 referred to in connection with FIG. 1A is effectively formed integrally with the cutting device 100. This is achieved by replacing the upper body portion 18 by a shorter upper body portion 118 so that it extends only about half way up the outside of the lower sleeve portion 62, omitting the upper sleeve portion 61, omitting the lower insert 87 of the go-devil 82, and directly screwing the lower end of the body 84 of the go-devil to threads 104 at the upper end of the lower sleeve portion 62. The remainder of the cutting device 100 is substantially identical to the cutting device 10.

In operation, the cutting device 100 is assembled round the line 12 at the top of the borehole, in a manner analogous to the assembly of the cutting device 10, and allowed to slide down the line under the influence of gravity. When the lower end of the cutting device 100 strikes the top of the stuck tool, the body 14 stops abruptly, but the go-devil 82 and the sleeve portion 62 continue moving downwardly under the influence of their combined inertia. This results in the sequence of events already described in relation to the cutting device 10, including the cutting of the line 12 and the clamping of the cutting device 100 to the severed part of the line 12.

Many modifications can be made to the described embodiment of the invention. For example, the movement of the blade member 30 in a counter clockwise direction can be limited by shear pins which extend through the blade member 30 on each side of the slot 52, into the blade member 28. Alternatively the movement of blade member 30 can be limited in a counter clockwise direction either by the lower end of sleeve portion 62 or by the lower end of the key bar 74 extending downwardly into contact with the upper end 53 of the blade member 30.

Since certain changes or modifications may be made in the disclosed embodiments without departing from the scope of the inventive concepts disclosed herein, it is the aim of the appended claims to cover all such 8 Changes and modifications falling within the true spirit and scope of the present invention.

We claim:

1. A cutting device adapted for cutting a flexible line 5 on which a well tool is suspended in a well, comprising: an elongated body having a longitudinally extending channel adapted to slidably receive the line to be cut; a first blade member fixedly mounted in said body and having a first surface defining a first cutting edge with a recessed middle portion, said first cutting edge being disposed around one side of said channel; a second blade member having a second surface slidably mounted on said first surface, said second surface defining a second cutting edge having a recessed middle portion, said second cutting edge being movable from a position around the opposite side of said channel along a path intersecting said channel substantially perpendicularly to the longitudinal axis thereof; and an actuating member engageable with said second blade member responsive to longitudinal force for causing sliding movement of said second blade member to cut the line, said first and second surfaces being coaxially disposed cylindrical surfaces with their common axes extending perpendicularly through the longitudinal axis of said channel, thereby producing a rotation of said second blade member about said common axis during said sliding movement.

2. The device of claim 1 wherein said first and second cutting edges have arcuate shapes substantially complementary with respective half-portions of the periphery of the line.

3. The device of claim 1 further comprising a relatively heavy inertial mass secured to said actuating member whereby the inertia of said mass is operative to apply said longitudinal force in response to a predetermined deceleration of said body when said body comes into contact with the well tool.

4. A cutting device adapted for cutting a flexible line upon which a well tool is suspended in a well, comprising: an elongated body having a longitudinally extending channel adapted to slidably receive the line so that said body can slide down the line and into contact with the well tool; a first blade member fixedly mounted in said body and having a first upper surface; a second blade member slidable relative to said first blade member and having a second lower surface which slides on said first surface along a path intersecting said channel substantially perpendicularly to the longitudinal axis thereof, said surfaces being coaxially disposed cylindrical surfaces with their common axes extending perpendicularly through the longitudinal axis of the channel to produce a rotation of said second blade member about said common axis during said sliding movement of said second surface on said first surface. said surfaces defining respective cutting edges with recessed middle portions disposed on opposite sides of said channel for enclosing a transverse cross-section of the cable prior to a cutting operation; an actuating member movable longitudinally in said body and engageable with said second blade member to produce said sliding movement of said second surface on said first surface whereby the cutting edge of said second blade member passes along said path through said channel to cut the line; and means responsive to the longitudinal movement of said actuating member for locking said device to the line above the cut.

5. The device of claim 4 wherein said cutting edges have concave shapes substantially complementary with respective half portions of the periphery of the cable.

6. The devices of claim 5 wherein said actuating member comprises a sleeve disposed coaxially within said body above the blade members and surrounding said channel, said sleeve being downwardly movable within said body into engagement with said second blade member for rotating said second blade member, and wherein said locking means comprises a locking member disposed inside said sleeve and adjacent to said channel, the internal surface of said sleeve being shaped to force said locking member into engagement with the cable in said channel during downward movement of said sleeve within said body.

7. The device of claim 6 further including means incorporating at least one shear pin for initially holding said sleeve above the blade members, and a relatively heavy inertial mass secured to said sleeve, the inertia of said mass being preselected for shearing said pin upon contact of said device with the well tool, and for producing said downward movement of said sleeve within said body to cut the cable and clamp said sleeve in engagement with the cable.

8. The device of claim 7 wherein said locking member extends downwardly into engagement with said second blade member to hold said second blade member prior to a cutting operation, said second blade member being adapted to move said locking member upwardly with respect to said body during rotation of said second blade member produced by said downward movement of said sleeve.

9. A cutting device adapted for cutting a cable or the like on which a well tool is suspended in a well having a gas-liquid interface, the device comprising: an elongated body having a longitudinally extending channel 'for receiving the cable, said body being adapted to slide down the cable into contact with the well tool; a first blade member fixedly mounted in the body and having a first surface defining a first cutting edge disposed on one side of said channel; a second movable blade member having a second surface slidably mounted on said first surface, said second surface defining a second cutting edge movable from a first position around the opposite side of said channel along a path intersecting said channel; an actuating member projecting upwardly above the body and downwardly movable from an upper position in said body for engaging said movable blade member to produce said movement of said second cutting edge across said channel; releasable holding means for maintaining said actuating member in said upper position, said holding means being effective for maintaining said operating member upon deceleration of said body due to impact of said body on the gasliquid interface; and a relatively heavy inertial mass having a channel therein for receiving the cable, said mass beind adapted to slide down the cable, independently of and above said body, for striking said upwardly projecting operating member to release said holding means and produce said downward movement of said operating member to cut the cable.

10. The device of claim 9 wherein said first and second surfaces are coaxially disposed cylindrical surfaces with their common axis extending perpendicularly to the longitudinal axis of said channel whereby said path intersects said channel substantially perpendicularly to the longitudinal axis thereof.

11. The device of claim 9 wherein said first and second cutting edges have arcuate shapes corresponding to half portions of the periphery of the cable for respectively enclosing a transverse cross-section of the cable when said second cutting edge is in said first position.

12. The device of claim 9 wherein said releasable holding means comprises a locking member longitudinally movable relative to said actuating member and engaging said second blade member, and means including a shear pin for releasably securing said locking member to said actuating member, thereby maintaining said actuating member in said upper position and said second blade member in said first position.

13. The device of claim 12 wherein said locking member is disposed adjacent to said channel against an inclined surface of said actuating member adapted to force said locking member into engagement with the cable in said channel during downward movement of said actuating member relative to said locking member after shearing of said pin to thereby clamp said actuating member to the severed cable. 

1. A cutting device adapted for cutting a flexible line on which a well tool is suspended in a well, comprising: an elongated body having a longitudinally extending channel adapted to slidably receive the line to be cut; a first blade member fixedly mounted in said body and having a first surface defining a first cutting edge with a recessed middle portion, said first cutting edge being disposed around one side of said channel; a second blade member having a second surface slidably mounted on said first surface, said second surface defining a second cutting edge having a recessed middle portion, said second cutting edge being movable from a position around the opposite side of said channel along a path intersecting said channel substantially perpendicularly to the longitudinal axis thereof; and an actuating member engageable with said second blade member responsive to longitudinal force for causing sliding movement of said second blade member to cut the line, said first and second surfaces being coaxially disposed cylindrical surfaces with their common axes extending perpendicularly through the longitudinal axis of said channel, thereby producing a rotation of said second blade member about said common axis during said sliding movement.
 2. The device of claim 1 wherein said first and second cutting edges have arcuate shapes substantially complementary with respective half-portions of the periphery of the line.
 3. The device of claim 1 further comprising a relatively heavy inertial mass secured to said actuating member whereby the inertia of said mass is operative to apply said longitudinal force in response to a predetermined deceleratioN of said body when said body comes into contact with the well tool.
 4. A cutting device adapted for cutting a flexible line upon which a well tool is suspended in a well, comprising: an elongated body having a longitudinally extending channel adapted to slidably receive the line so that said body can slide down the line and into contact with the well tool; a first blade member fixedly mounted in said body and having a first upper surface; a second blade member slidable relative to said first blade member and having a second lower surface which slides on said first surface along a path intersecting said channel substantially perpendicularly to the longitudinal axis thereof, said surfaces being coaxially disposed cylindrical surfaces with their common axes extending perpendicularly through the longitudinal axis of the channel to produce a rotation of said second blade member about said common axis during said sliding movement of said second surface on said first surface, said surfaces defining respective cutting edges with recessed middle portions disposed on opposite sides of said channel for enclosing a transverse cross-section of the cable prior to a cutting operation; an actuating member movable longitudinally in said body and engageable with said second blade member to produce said sliding movement of said second surface on said first surface whereby the cutting edge of said second blade member passes along said path through said channel to cut the line; and means responsive to the longitudinal movement of said actuating member for locking said device to the line above the cut.
 5. The device of claim 4 wherein said cutting edges have concave shapes substantially complementary with respective half portions of the periphery of the cable.
 6. The devices of claim 5 wherein said actuating member comprises a sleeve disposed coaxially within said body above the blade members and surrounding said channel, said sleeve being downwardly movable within said body into engagement with said second blade member for rotating said second blade member, and wherein said locking means comprises a locking member disposed inside said sleeve and adjacent to said channel, the internal surface of said sleeve being shaped to force said locking member into engagement with the cable in said channel during downward movement of said sleeve within said body.
 7. The device of claim 6 further including means incorporating at least one shear pin for initially holding said sleeve above the blade members, and a relatively heavy inertial mass secured to said sleeve, the inertia of said mass being preselected for shearing said pin upon contact of said device with the well tool, and for producing said downward movement of said sleeve within said body to cut the cable and clamp said sleeve in engagement with the cable.
 8. The device of claim 7 wherein said locking member extends downwardly into engagement with said second blade member to hold said second blade member prior to a cutting operation, said second blade member being adapted to move said locking member upwardly with respect to said body during rotation of said second blade member produced by said downward movement of said sleeve.
 9. A cutting device adapted for cutting a cable or the like on which a well tool is suspended in a well having a gas-liquid interface, the device comprising: an elongated body having a longitudinally extending channel for receiving the cable, said body being adapted to slide down the cable into contact with the well tool; a first blade member fixedly mounted in the body and having a first surface defining a first cutting edge disposed on one side of said channel; a second movable blade member having a second surface slidably mounted on said first surface, said second surface defining a second cutting edge movable from a first position around the opposite side of said channel along a path intersecting said channel; an actuating member projecting upwardly above the body and downwardly movable from an upPer position in said body for engaging said movable blade member to produce said movement of said second cutting edge across said channel; releasable holding means for maintaining said actuating member in said upper position, said holding means being effective for maintaining said operating member upon deceleration of said body due to impact of said body on the gas-liquid interface; and a relatively heavy inertial mass having a channel therein for receiving the cable, said mass beind adapted to slide down the cable, independently of and above said body, for striking said upwardly projecting operating member to release said holding means and produce said downward movement of said operating member to cut the cable.
 10. The device of claim 9 wherein said first and second surfaces are coaxially disposed cylindrical surfaces with their common axis extending perpendicularly to the longitudinal axis of said channel whereby said path intersects said channel substantially perpendicularly to the longitudinal axis thereof.
 11. The device of claim 9 wherein said first and second cutting edges have arcuate shapes corresponding to half portions of the periphery of the cable for respectively enclosing a transverse cross-section of the cable when said second cutting edge is in said first position.
 12. The device of claim 9 wherein said releasable holding means comprises a locking member longitudinally movable relative to said actuating member and engaging said second blade member, and means including a shear pin for releasably securing said locking member to said actuating member, thereby maintaining said actuating member in said upper position and said second blade member in said first position.
 13. The device of claim 12 wherein said locking member is disposed adjacent to said channel against an inclined surface of said actuating member adapted to force said locking member into engagement with the cable in said channel during downward movement of said actuating member relative to said locking member after shearing of said pin to thereby clamp said actuating member to the severed cable. 